Conventional optical microscopes may be compared to a willow tree. The sample positioning stage, illumination system, optical observation system and other components mounted on the main stand (corresponding to the trunk of the tree) lack balance and are asymmetrical about the optical axis in both mass and shape. Such an unstable structure is shown in FIG. 1. In FIG. 1, 101 is a television camera, 102 is a relay lens, 103 is a connecting tube, 104 denotes a straight tube, 105 denotes an eyepiece, 106 denotes a binocular tube, 107 denotes a lens mount, 108 denotes a light source for fluorescence excitation, 109 denotes an incident-light fluorescence equipment, 110 denotes an arm, 111 denotes a revolver, 112 denotes an objective lens, 113 denotes a stage, 114 denotes a vertical adjustment mechanism, 115 denotes a condenser, 116 denotes a main stand, and 117 denotes a base and illumination system.
A conventional optical microscope as shown in FIG. 1 comprises a base and a illumination system at the bottom, with one end installed on the main stand. An arm is supported on the side of the upper end of the main stand, basically forming a U-shaped structure. The main stand supports the vertical adjustment mechanism for the sample mounting stage. A condenser is set under the stage to guide illumination light from the illumination system to the sample being observed. The objective lens with a revolver to choose the lens magnification is mounted under the arm. The incident-light fluorescence equipment, lens mount, straight tube, relay lens, and TV camera are installed above the arm. The light source for fluorescence excitation is attached to the side of the incident-light fluorescence device. The binocular tube and eyepiece are mounted on the side of the lens mount. In addition, the accessory measuring units, cameras, and other devices are mounted like “branches and leaves” on a tree. The important components of an optical photometric system and optical imaging system, corresponding to the trunk of the tree, are unstable because the main stand is set on one end of the base and the illumination system. This cantilever structure makes not only the “branches and leaves” but also the thin “trunks” to sway like a willow tree.
In the conventional optical microscope, a half-mirror (including dichroic mirror) is typically installed on the inlet of the illumination system (incident-light fluorescence, total internal reflection fluorescence, transmitted light fluorescence, incident polarized light, transmitted polarized light, bright field incidence, optical tweezers, and etc.) and also on the inlet of the optical monitor system. A single imaging lens is, however, commonly used to reduce cost. The support fixtures for the illumination system are integrated with the optical imaging and photometric systems, with the result that instability caused by asymmetry in the shape and mass of the support fixtures for the illumination and monitor systems and shrinkage/elongation of those support fixtures due to temperature dependency bring about the fluctuation of the optical axis in the optical imaging and photometric systems.
A new field of study called single-molecule physiology is becoming popular. In this science, the motion of protein and other biological molecules is observed and controlled. Optical microscopes are essential tools in this study and they require accuracy of several nanometers for effective analysis because the motions of the biological substances are minute.
Currently available optical microscopes are not stable enough and drift occurs during observation, recording and measurement performed for extended times. The observation results are always subject to errors.
The present invention offers a highly stable optical microscope that is free from defocusing of samples and displacement (drift) of the object point (object) during observation. A dedicated, rather than common, imaging lens is mounted for each optical system headed by an imaging lens.
By installing a dedicated imaging lens for each system, for example the television camera system, the center of the imaging lens and focal position are displaced together. This principle is described below referring to FIGS. 2A and 2B.
Assume displacement in the X-Y direction occurs as shown in FIG. 2B relative to the ideal position shown in FIG. 2A due to the effects of instability caused by asymmetry in the shape and mass of the support fixtures. Since the imaging lens and television camera are integrated, the object is successfully imaged without relative displacement of the center of the imaging lens and the focal position, although light flux is somewhat deviated.
This is an application of the principle of astronomical telescopes. There is no displacement, parallel or perpendicular to the optical axis, of the image of the object relative to the imaging lens, provided that the telescope only translates without inclination.